stall when giving gas

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
got a 86 4.3 4 blr rochester when I idle its fine but when you give it gas after 30 seconds it stalls and dies then i restart the motor its idles fine then give it gas it goes for 10 seconds this time and dies the longer i idle the more time i get before it dies at half throttle as if its the pump or water seperater its starving for gas.<br /> Now the engine was replaced and the manifold sat outside a few days before going the new used motor but i dont think water got in the carb can i spray it with carb cleaner or should i put dry gas in the carb and let it sit. <br />I have the old fuel pump that was on the blown motor should i put it on cause I know it was good or could it be the carb i just dont want to go chasing this problem and rebuild the carb for nothing my guess is the pump what do you think????? <br />Could it be the interupt switch miss aligned or I wired it up for the first time before i did the motor i did not have a boat manual and notice in the manual that a white a green wire goes to the interupt switch and the other white and green goes to the distributor which in the manual you supposed to do? Well before I did the motor I had both green and white wires going to the interrupt switch which is wrong acording to the manual but it ran fine but had troulble going to reverse and foward my other guess is since I have done the wiring diferently but to manual spec that this could be the problem when moving the throttle in ingaged the interupt switch maybe???
 

medic

Petty Officer 2nd Class
Joined
May 18, 2003
Messages
111
Re: stall when giving gas

what king of engine? not sure if you are having the same problems as myself and a couple of others, but ours would stall after about 40 min. of use. i am getting ready to replace ignition coil.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

its a 4.3 the coil was fine before a week ago i can get a used one from the old engine let me know how you make out asap jayvette75@yahoo.com
 

magster65

Commander
Joined
Sep 1, 2002
Messages
2,573
Re: stall when giving gas

Sometimes a vapor lock or bad anti-siphon valve will do that. There's been a couple posts on that similar problem lately.
 

McKenzie

Petty Officer 2nd Class
Joined
Apr 25, 2003
Messages
192
Re: stall when giving gas

sounds like a restriction in the fuel system. Most likely the fuel pump isn't flowing enough. At idle the engine isn't using that much fuel and the fuel pump can keep up with its demands. Once you throttle up, the engine empties the fuel bowl (that the fuel pump should keep full), and you stall out. Thats my guess.
 

chris in va

Chief Petty Officer
Joined
May 4, 2003
Messages
410
Re: stall when giving gas

I agree with McKenzie. Sounds like your inlet needle inside the bowl isn't allowing enough gas in, and the engine just sucks it out of the bowl. It's very easy to take the bowl off and check it.<br /><br />Something else could be blocking fuel flow too however. Fuel filter(s)?
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

I will put the old fuel pump back and switch the wires the go to the interupt switch /distributor I may have them backwards cause i may be ingaging the switch when i move the throttle foward.The wires and pump are the only new items since i put the engine in so the old pump that came with the engine could be bad or the wiring.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

ok i have disconnected my interupt switch and install a known good fuel pump and a known coil that is good. Now I looked at the distributor cap it was a bit moist it not the old cap its the one that came with the motor and the black contact ball on the top of the disributor cap that the rotor hit seems a bit worn and there was moisture on the rotor and cap but they were dried. Now I idle the boat at 2000 rmp for 40 seconds then it dies then I restart it I idle around for 1 min then it dies I restart it idle around and when i goose it it dies after 5 seconds also when i rev in neutral for 40 seconds minute and it dies i have trouble restarting it so i wait for 10 seconds then it starts right up one last thing the negitive cables were hot as hell what is the PROBLEM???????
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

does any think it could be the ditributor cap
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

I just found out the wires were crossed on the altenator<br />the purple wie that goes to the coil and the wire that goes to the the ignition were worng on the back of the alt i did not think it amde a difference but i will try it i though on the back of the alt there are both positive but will see you have 4 contacts 1 neg 2 orange to the starter 3 red/purple the ignition purple to the pos coil could that be the problem alck power and causing the motor to cut off at 2000 rpm and above
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

well it was not the altenator it was not the tach i am getting a new cap rotor wires and sensor for ignition hope that is after that it must be fuel or something in the throttle killing the ignition
 

DaveM

Petty Officer 1st Class
Joined
Feb 27, 2002
Messages
308
Re: stall when giving gas

I'm not very familiar with that year engine, but is sounds like a fuel issue. It could be either a problem with fuel delivery or the carb. You might consider replacing the fuel pump and anti-siphon valve, both can cause perplexing, intermittent failures.
 

Stanp

Seaman Apprentice
Joined
Jul 30, 2002
Messages
49
Re: stall when giving gas

have a 4.3 omc that stalled as would throttle up. It acted like it was starved of fuel. I changed the water seperator filter and the problem has not come back. I also pulled the filter at the carb, but it was clean. I had the carb rebuilt 2 yrs ago. You might consider rebuilt carb if new fuel seperator doesn't work. Those interuptor switches, check and recheck. Mine were loose, that is the screws were loose but I don't think they were the problem - they were sure at the top of the list if the fuel seperator didn't work.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

I will disconnect the line and run it to the pump directly as a test. I have replaced the distributor cap wires and sensor so i will test it in the morning
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

does any one think it could be my thunderbolt IV ignition failing at highier outputs or it would not work at all
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Re: stall when giving gas

Its Over I bought a used distributor on ebay giving me a cap rotor sensor wires and a coil all for 70.00 the boat runs great !!!!full power!!!!!!!!!!!!!!
 
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